What does defanging an IP address mean?

It means replacing every period '.' in an IPv4 address with '[.]' to prevent accidental execution or parsing issues.

Which string-driven strategy is best for this problem?

Direct replacement using built-in functions is simplest, but iterative concatenation ensures precise control over each character.

Can I use regular expressions for defanging an IP address?

Yes, but simple replace or split/join methods are more readable and less error-prone for small IPv4 strings.

What is the time and space complexity of defanging an IP?

Both time and space complexity are O(n), where n is the length of the input string, since every character is processed and a new string is created.

Are there any edge cases to consider?

Yes, ensure the input is a valid IPv4 address and all periods are replaced exactly once without adding extra characters.

#1108

Easy

auto_awesomeString-driven solution strategy

LeetCode 题解工作台

IP 地址无效化

给你一个有效的 IPv4 地址 address ，返回这个 IP 地址的无效化版本。所谓无效化 IP 地址，其实就是用 "[.]" 代替了每个 "." 。示例 1：输入： address = "1.1.1.1" 输出： "1[.]1[.]1[.]1" 示例 2：输入： address = "…

字符串

题目描述

给你一个有效的 IPv4 地址 address，返回这个 IP 地址的无效化版本。

所谓无效化 IP 地址，其实就是用 "[.]" 代替了每个 "."。

示例 1：

输入：address = "1.1.1.1"
输出："1[.]1[.]1[.]1"

示例 2：

输入：address = "255.100.50.0"
输出："255[.]100[.]50[.]0"

提示：

给出的 address 是一个有效的 IPv4 地址

lightbulb

解题思路

方法一：直接替换

我们直接将字符串中的 '.' 替换为 '[.]' 即可。

时间复杂度 $O(n)$ ，其中 $n$ 为字符串的长度。忽略答案的空间消耗，空间复杂度 $O(1)$ 。

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class Solution:
    def defangIPaddr(self, address: str) -> str:
        return address.replace('.', '[.]')

speed

复杂度分析

指标	值
时间	complexity is O(n) where n is the length of the input string since each character is processed once. Space complexity is also O(n) because a new string is created for the defanged IP.
空间	Depends on the final approach

psychology

面试官常问的追问

外企场景

question_mark
Checks understanding of string manipulation basics and built-in methods.
question_mark
Wants clarity on iteration versus built-in replacements.
question_mark
Looks for awareness of edge cases with input formatting.

warning

常见陷阱

外企场景

error
Forgetting to replace all periods, only handling the first occurrence.
error
Adding extra characters or incorrect brackets, like '[..]' instead of '[.]'.
error
Using regex incorrectly, causing unintended replacements or errors.

swap_horiz

进阶变体

外企场景

arrow_right_alt
Defang IP addresses with alternative separators like '<.>' instead of '[.]'.
arrow_right_alt
Handling mixed IPv4 and IPv6 addresses, applying defanging only to IPv4 parts.
arrow_right_alt
Return defanged address while also validating correct IPv4 formatting before transformation.

help

常见问题

外企场景

继续练习

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